Previously errors while disconnecting volumes from the source host
during post_live_migration within LibvirtDriver would result in the
overall failure of the migration. This would also mean that while the
instance would be running on the destination it would still be listed as
running on the source within the db.
This change simply ignores any exceptions raised while attempting to
disconnect volumes on the source. These errors can be safely ignored as
they will have no impact on the running instance on the destination.
In the future Nova could wire up the force and ignore_errors kwargs when
calling down into the associated os-brick connectors to help avoid this.
NOTE(mriedem): The driver.py change is slightly different from Train
because pep F841 was not enforced starting in Train but is in Stein.
Closes-Bug: #1843639
Change-Id: Ieff5243854321ec40f642845e87a0faecaca8721
(cherry picked from commit ac68cffd43)
(cherry picked from commit ff36b6d97f)
022ea28194